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ABSTRACT: Normal-hearing (NH) listeners and hearing-impaired (HI) listeners detected and discriminated time-reversed harmonic complexes constructed of equal-amplitude harmonic components with fundamental frequencies (F0s) ranging from 50 to 800 Hz. Component starting phases were selected according to the positive and negative Schroeder-phase algorithms to produce within-period frequency sweeps with relatively flat temporal envelopes. Detection thresholds were not affected by component starting phases for either group of listeners. At presentation levels of 80 dB SPL, NH listeners could discriminate the two waveforms nearly perfectly when the F0s were less than 300-400 Hz but fell to chance performance for higher F0s. HI listeners performed significantly poorer, with reduced discrimination at several of the F0s. In contrast, at a lower presentation level meant to nearly equate sensation levels for the two groups, NH listeners' discrimination was poorer than HI listeners at most F0s. Roving presentation levels had little effect on performance by NH listeners but reduced performance by HI listeners. The differential impact of roving level suggests a weaker perception of timbre differences and a greater susceptibility to the detrimental effects of experimental uncertainty in HI listeners.
Journal of the Association for Research in Otolaryngology 09/2009; 10(4):609-19. · 2.84 Impact Factor
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ABSTRACT: Reduced ability to make use of temporal fine structure (TFS) information may contribute to deficits among hearing impaired (HI) listeners for speech recognition in competing background sounds. The broad tuning typically observed in HI listeners will produce more complex patterns of TFS as input to the auditory nerve, and these patterns may be more difficult to encode andor interpret by higher auditory centers. In the current study, we tested HI listeners on a frequency-modulation (FM) detection task thought to require the use of TFS cues, on tone detection in notched-noise to assess frequency selectivity, and on speech recognition in continuous and modulated background sounds. Performance on the psychoacoustic tasks was tested at four frequencies (500, 1000, 2000, and 4000 Hz) at levels between 60 and 85 dB SPL (approximating the range of third-octave band levels in the speech stimuli). HI listeners with similar audiometric thresholds showed clear differences in frequency tuning, FM detection thresholds, and speech performance. Relationships between the psychoacoustic measures in the four frequency regions and between these measures and speech performance will be discussed.
The Journal of the Acoustical Society of America 05/2009; 125(4):2632. · 1.55 Impact Factor
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ABSTRACT: Anthropogenic noise (e.g., highway noise) that exceeds natural ambient sound levels potentially can mask important acoustic signals used by birds during communication. Signals degraded by masking can in turn adversely affect critical behaviors such as mate attraction, territorial defense, parent-offspring communication, predator avoidance, and prey detection. The amount of masking depends not only on the physical characteristics of the noise (intensity, frequency, temporal pattern, etc.) but also the auditory capacity of the species, the acoustic structure of their vocal signals, the proximity of the birds to the noise source and each other, and the sound attenuation properties of the habitat. Here we present a quantitative model for predicting effective communication distances between birds subject to different levels and types of anthropogenic noise. Cross-species analysis shows that communication distances are largely contextenvironment dependent and species specific. Extrapolation of noise impact distance estimates even within groups of similar species should be exercised with caution. This model should be useful in environmental impact analysis of anthropogenic noise on birds and other wildlife, particularly species of conservation concern.
The Journal of the Acoustical Society of America 05/2009; 125(4):2517. · 1.55 Impact Factor
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ABSTRACT: Belgian Waterslager canaries (BWC), bred for a distinct low-pitched song, have an inherited high-frequency hearing loss associated with hair cell abnormalities. Hair cells near the abneural edge of the papilla, which receive primarily efferent innervation in normal birds, are among the most severely affected. These cells are thought to support nonlinear active processing in the avian ear, though the mechanisms are poorly understood. Here we present psychophysical evidence that suggests degraded active processing in BWC compared to normal-hearing non-BWC. Critical ratios, psychophysical masking patterns and phase effects on masking by harmonic complexes were measured in BWC and non-BWC using operant conditioning procedures. Critical ratios were much larger in BWC than in non-BWC at high frequencies. Psychophysical tuning curves derived from the masking patterns for BWC were broadened at high frequencies. BWC also showed severely reduced phase effects on masking by harmonic complexes compared to non-BWC. As has been hypothesized previously for hearing-impaired humans, these results are consistent with a loss of active processing mechanisms in BWC.
Journal of Comparative Physiology 01/2009; 195(2):193-202. · 2.01 Impact Factor
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